Printing processes serve not only to reproduce and transmit objective information, but also to convey esthetic impressions, for example when coffee-table books are printed or else in pictorial advertising. An immense problem here is posed in particular by the reproduction of metallic hues. Metallic hues are only imperfectly reproducible by a color mixture formed from primary colors, especially the colors cyan, magenta, yellow, and black (CMYK). A gold tone is particularly difficult to reproduce by means of such a color mixture. It has therefore already been proposed to incorporate metallic pigments or particles in the printing ink in order that a metallic color may be brought about directly. But in the case of toners, where magnetic and/or electrical and especially electrostatic properties are decisive, this is particularly problematic, since metallic constituents may have an adverse effect on these properties. Yet there have already been proposals to imbue toners with metallic constituents. For instance, U.S. Pat. No. 5,180,650, issued on Jan. 19, 1993, discloses providing a toner composition, which contains lightly colored metallic constituents, such as copper, silver or gold for example, in a coating, which in turn has been provided with an over-coating comprised of a metal halide.
But the appearance of prints in particular may be adversely affected by chemical reactions of the metallic constituents due to the halides, which can promote oxidations of the constituents for example. For instance, the tarnishing with which everyone is familiar from copper or silver objects may occur, making the metallic quality unattractive or disappear completely. Moreover, these toners are only lightly metallically colored, which is insufficient to reproduce a gold tone in printed matter. Further, when metallic constituents are incorporated in toners using conventional manufacturing processes, these metallic flakes are randomly oriented throughout the toner particles. This random orientation leads to the loss of metallic hue, and causes a dark appearance when such toners are fixed to a receiver sheet using heated rollers.